Overdrive transmission



Aug. 25, 1942'. R. F. STALLMAN 2,294,216

OVERDRIVE TRAMSMISSION I Filed'Aug: 16, 1939 INVENTOR. 7 RALPH F STALL MAN 28 By ATTORNEY Patented Aug. 25, 1942 UNITED STTES PATENT OFFICE OVERDRIVE TRANSMISSION Ralph F. Stallman, San Francisco, Calif. Application August 16, 1939, Serial No. 290,445

8 Claims.

The present invention relates to transmissions and particularly to an auxiliary transmission usually referred to as overdrive, employed in automobiles to obtain a gear ratio higher than that of conventional high gear.

Many automobiles are sold Without an overdrive transmission and some are sold with an overdrive transmission which may be installed at the option of the purchaser, while in other makes of automobiles where the manufacturer does not provide for such a transmission, it is common practice for manufacturers of accessory.

devices for automobiles to make up transmissions of this type for installation.

It is therefore desirable that an overdrive transmission be designed for installation in automobiles with as little change as possible in arrangement of the conventional parts, and that it be made in such a manner that it can readily be adapted to automobiles of different makes.

It is an object of the present invention to provide a transmission that may be placed in an automobile with a minimum of mechanical alteration.

A further object is the provision of a transmission for automobiles that will be principally supported between two fixed points such as the centers of the conventional universal joints in a propeller shaft, and which need not therefore take support from any part of the frame.

A further object is the provision of a transmission of Very simple and inexpensive construction with constantly meshing gears adapted to be controlled to effect a direct or overdrive, and to provide means for preventing the transmission being operated in overdrive except when the conventional automobile transmission is in its high gear position and to accomplish automate shifting of the overdrive transmission to direct drive in the event the conventional transmission is shifted from high gear to first or second gear.

A further object is the provision of a connection for a speedometer having two gear ratios in order to compensate for the difference between direct and overdrive power transmission and means for effecting automatic shifting of this speedometer connection upon shifting of the overdrive transmission.

One form of the invention is illustrated in the accompanying drawing, and reference to this drawing is made in the following specification, wherein further objects and advantages of the invention are made apparent.

In the drawing Fig. l is a plan view of a transmission constructed in accordance with the present invention and illustrated as assembled in position between the universal joints of a conventional automobile, parts of which are shown for purposes of illustration;

Fig. 2 is a horizontal sectional view through the transmission illustrated in Fig. 1; and

Fig. 3 is an enlarged detail of part of the mechanism illustrated in Fig. 2.

Referring to the drawing in detail, the transmission is shown as positioned between the forward universal joint if) and the rear universal joint ll of an automobile, and thus occupying the position ordinarily occupied by the propeller shaft which transmits power through these univarsal joints from the conventional transmission enclosed in the housing l2 to the conventional differential enclosed in the housing 13. While a specific type of universal joint is illustrated, it will be apparent from the following description that the transmission may be supported between any conventional connections designed for the purpose of transmitting universal movement.

Referring to Fig. 2, the overdrive transmission is shown as comprising a drive shaft l4 to the rear end of which is fixed a drum shaped internally toothed gear l5. A driven shaft l6 carries a pinion ll which meshes with the internal gear l5. The shafts i i and I5 are connected with the universal joints lo and M respectively,

and by virtue of the gears l5 and I1 being in' the difference in driving ratio is effected by causing the gear IE to drive the gear ll about its own axis or by causing the gear to carry the gear ll with it so that the gear 57 and shaft it are revolving not about their own axis but about the axis of the gear i5 and shaft M. 'The gears and shafts thus far described are encased by a housing which comprises a rear half to and a forward half I9 secured together as by bolts 28, which bolts also serve to clamp in position between the halves of the housing a wall or plate 2! in which there is an eccentrically positioned opening for the reception of a suitable bearing 22 which supports the forward end of the shaft 16. The for Ward housing part l9 contains a bearing 23 which likewise serves to support the shaft l i for rotation.

If the housing which includes the parts l8 and I9 is keyed to either of the shaftsid or l6 so that relative rotation between the housing and therein rotates relative to the housing and shafts is prevented, a direct drive will be imparted through the transmission. In order so to key or connect the housing with a shaft, the forward portion I9 of the housing is bored for the reception of a pin which is reciprocable within limits defined by a stop pin 26 and a slot 21. The rear end of the pin 25 is engageable upon the pin being moved rearwardly with notches 23 formed in the periphery of the gear I5. The notches may be spaced at suitable intervals, although a single notch or two notches spaced 180 will be adequate. When the pin 25 is engaged with any of the notches 28, the gear I5 and consequently the shaft I4 to which it is fixed are locked against rotation relative to the housing. Consequently, when the drive shaft rotates, it carries with it the housing part I9 as well as the part I8 and the intermediate plate 2|. The eccentric bearing opening in the plate 2i consequently moves with the gear I5 and the gears I5 and II are relatively fixed so that the driven shaft I6 rotates at the same speed as the drive shaft I4. A suitable counterweight 18a may be provided interiorly of the housing part I3 to compensate for the eccentric position of the shaft l6 and to overcome any tendency toward excessive vibration that would result from the revolving of this shaft about the axis of the drive shaft I4.

In order to effect overdrive at a rate which depends upon the ratio between the gears I5 and II, the casing is freed from its connection with the shaft and is locked against rotation. This is efiected through the medium of a torque sleeve mounted for reciprocal movement longitudinally of the shaft I4. This torque sleeve 30 fits slidably over the forward end of the casing part I8 and has a bushing 3| in its forward end which is slidably and rotatably fitted to the shaft I4. A torque arm 32 is pivotally connected as at 33 with the torque sleeve 30 and pivotally or otherwise loosely connected as at 34 to a suitable bracket fixed to the frame of the automobile, a portion of which frame is indicated at 35 in Fig. I. The torque arm 32 serves at all times to pre ventrotation of the torque sleeve 30] but to permit longitudinal sliding movement thereof relative to the shaft I4. Toward its rear end the torque sleeve 35 is provided with a pair of external annular integrally formed collars 35 and 31. The collar 36 engages between a fixed collar 38 on the pin 25 and a sliding collar 39 on said pin, the collar 39 being urged toward the rear end of the pin by a spring interposed between the collar and a head 4| on the pin, as is most clearly shown in Fig. 3 of the drawing.

The collar 31 on the torque sleeve 35 is provided with peripherally spaced notches 42 shaped to register with the collar 38 on the pin 25 and thus to form a lock between the torque sleeve and the housing part I9 by which the pin 25 is carried. In order to shift from the direct drive position illustrated in Fig. 2 to overdrive position, the torque sleeve 35 is moved forwardly. Upon such movement the collar 36 on the torque sleeve engages collar 39, withdrawing the pin 25 from its connection with the gear I5, then compressing the spring 45 until the collar 3'! aligns with the collar 38, with the latter collar being received in one of the notches 42. In this position the housing is locked against rotation with respect to the torque sleeve which, in turn, is prevented from rotating by means of the torque arm 32. Now upon rotation of the drive shaft I4, the gear I5 plate 2I, which is fixed to the housing, holds the bearing 22 in a fixed position, the gear I! is rotated about its own axis, imparting rotation to the shaft I6 at a speed greater than that of the shaft I4.

Adjacent the forward end of the shaft I4 are a pair of speedometer worms 43 and 44 adapted to mesh with a gear 45 which is fixed in the conventional manner to the end of the cable 46 (see Fig. 1), which transmits rotary movement from the drive shaft to the speedometer. As the gear 45 is carried by the torque sleeve 30, sliding movement of this sleeve in the shifting operations described above effects shifting of this gear from one to the other of the worms 43 and 44. These worms are pitched to compensate the speed of rotation of the speedometer cable with the difference in ratio produced in shifting the overdrive. The pitch of the worms 43 and 44 varies but slightly, and in order that both worms will mesh with the single gear 45, this gear is out twice; that is to say, it is cut first with a cutter corresponding in pitch to the worm having the least pitch and then re-cut with a cutter corresponding in pitch to the other worm. With this system of cutting the gear 45, one of the worms will mesh with one half of all of the gear teeth, and the other will mesh with the other half of the teeth.

In order that the transmission may conveniently be shifted from the operators seat of the automobile, there is connected to the torque arm 7 32 a link 55, the forward end of which is connected by a light tension spring 5I to a suitable anchorage on the motor as shown, or on any convenient fixed part of the automobile. A bracket 52 may be provided for guiding the forward end of the link 55. of the link 55 a sliding collar 53 carries a pin 54 to which is pivoted an actuating lever 55. A compression spring 53, heavier than the spring 5I, is interposed between the sliding collar 53 and a collar 5'! fixed to the link 55. The actuating lever 55 is provided with a fulcrum lug 58 intermediate its ends and is connected to its outer end with a Bowden cable 59 of conventional structure which may lead to the instrument panel or other convenient position adjacent the operators seat, and which terminates in a control knob 65. Upon the control knob 60 being pulled outwardly, the lever 55 is pivoted about its fulcrum lug 58 and, through the collar 53 and the compression spring 55, imparts rearward movement to the link 55, which in turn moves the torque sleeve 35 to the rear through the medium of the torque arm 32, thus shifting the transmission to its overdrive position. Upon pushing the control knob 60 inwardly, the pressure on the compression spring 56 is released and the tension spring 5I operates to shift the transmission back to direct or conventional drive.

It is desirable that the overdrive be operable only when the main transmission is in high gear, and the present invention contemplates means for preventing operation of the overdrive except when the automobile is operating in high gear, and furthermore, it provides for automatic shifting of the transmission from overdrive to direct drive in the event that the main transmission is shifted from high gear back to second or first. To this end the fulcrum lug 58 on the actuating lever 55 operates against the end of a lever 5|. This lever is fixed to a pin 62 which is rotatably journalled in the top of the housing I2 which encloses the main trans- Intermediate the ends mission of the automobile. The main transmission includes the customary band shown in dotted lines at 63, and the pin 52 is connected to this band by a lever 64 within the housing I 2. When the main transmission is shifted to its high gear position, the shift band 63 moves forwardly and through the lever 6| turns the pin 62 and swings the lever 6| thereon to the position shown in which its end serves as pivot point for the fulcrum lug 58. Upon shifting of the main transmission to any other position, the lever 6| is swung away from the lug 58, with the result that the actuating lever 55 can not be actuated to shift the transmission to its overdrive position because it has no fulcrum point upon which to swing. Furthermore, if the auxiliary transmission was in overdrive when the main transmission was shifted out of high gear, the lever 6| would move away from the lug 58, thus permitting the spring 5| automatically to shift the auxiliary transmission to its direct drive position. One of the important features of the present invention is that the auxiliary transmission is connected to and entirely supported by the universal joints which ordinarily support the propeller shaft, and receives no support from any other part of the automobile. This provides for easy installation and makes the transmission readily adaptable to automobiles of different sizes and types. arm '32 connects with the frame, and parts of the operating mechanism are connected to other parts of the vehicle, none of these parts serves to support any of the weight of the transmission itself.

The transmission as herein illustrated and described is designed for use in an automobile to provide an overdrive or a driving ratio higher than high gear in the main transmission. It is to be understood, however, that the invention is not limited to the specific structure or use illustrated, as it is readily adaptable to trucks or other heavy vehicles and can, upon reversal of its operating parts, function as an underdrive to provide gear ratios lower than those provided by the main transmission of the vehicle.

In order to cause the transmission to operate as an underdrive, it is simply necessary to reverse the positions of its connections with the universal joints l0 and H. The torque arm 32 would then connect with the frame 35 approximately opposite the rear universal joint II and the rod 50 would be extended the amount necessary to effect connections with the torque arm.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a transmission of the character described, a drive shaft, a driven shaft, gears connecting said shafts for operation in direct or overdrive ratio, a housing rotatably supported with respect to one of said shafts, means to key the housing to said shaft to effect a direct drive and means to prevent rotation of the housing to effect an overdrive.

2. In a transmission of the character described, a drive shaft with a large gear thereon,

While the torque I a driven shaft with a small gear meshing with said large gear, a housing embracing the gears and maintaining the gears in mesh, means for locking the housing to said large gear for rotation therewith whereby the small gear will travel with the large gear and means for locking the housing against rotation whereby the large gear will impart rotation to the small gear.

3. In an auxiliary transmission for automobiles including means for changing the driving ratio, a speedometer connection comprising a pair of gears of different pitch to compensate for changes in driving ratio, a worm adapted to mesh with either of said gears and means for shifting said worm to mesh selectively with said gears automatically upon changing the driving ratio.

4-. In a transmission of the character described, a pair of shafts, gears connecting said shafts, a rotatable housing enclosing said gears, said shafts, gears, and housing being adapted to be supported by and between the conventional universal joints of an automobile, and a torque arm engaging a fixed part of the automobile and associated with means selectively to permit or prevent rotation of the housing.

5. In a transmission of the character described, a pair of shafts, gears connecting said shafts, a rotatable housing enclosing said gears, said shafts, gears, and housing being adapted to be supported by and between the conventional universal joints of an automobile, a torque sleeve slidably embracing one shaft, a torque arm engaging between said sleeve and the frame of the automobile, and means to lock the housing relative to the torque sleeve upon sliding movement of the latter.

6. A transmission for automobiles adapted to occupy the position between two universal joints ordinarily occupied by a propeller shaft comprising, an internal ring gear on an axis aligned with both universal joints, a pinion gear in constant mesh with the ring gear and rotating on an axis aligned with only one of said joints, and means for changing the gear ratio of said transmission without disengaging said gears.

7. A transmission for automobiles adapted to occupy the position between two universal joints ordinarly occupied by a propeller shaft comprising, one gear rotatable on an axis aligned with both universal joints a second gear in constant mesh with said one gear and rotatable on an aXis aligned with only one of said joints, and means for changing the gear ratio of said transmission without disengaging said gears.

8. A transmission adapted to be positioned between and receive its principal support from the two universal joints which normally support the propeller shaft of an automobile comprising, one gear rotatable on an axis common to both said joints a second gear in constant mesh with said one gear and rotatable on an axis common to but one of said joints, and means for changing the gear ratio of said transmission without disengaging said gears.

RALPH F. STALLMAN. 

